Use a CacheIterator iterator.

spec/loophp/collection/CollectionSpec.php

@@ -17,8 +17,6 @@
 use loophp\collection\Operation\AbstractOperation;
 use OutOfRangeException;
 use PhpSpec\ObjectBehavior;
-use Psr\Cache\CacheItemInterface;
-use Psr\Cache\CacheItemPoolInterface;
 use stdClass;
 
 class CollectionSpec extends ObjectBehavior
@@ -226,86 +224,31 @@ public function it_can_be_returned_as_an_array(): void
             ->shouldIterateAs(['1', '2', '3']);
     }
 
-    public function it_can_cache(CacheItemPoolInterface $cache, CacheItemInterface $cacheItemFound0, CacheItemInterface $cacheItemNotFound1, CacheItemInterface $cacheItemNotFound2, CacheItemInterface $cacheItemNotFound3): void
+    public function it_can_cache(): void
     {
         $fhandle = fopen(__DIR__ . '/../../fixtures/sample.txt', 'rb');
 
-        $cache
-            ->getItem('1')
-            ->shouldBeCalledOnce();
-        $cache
-            ->getItem('2')
-            ->shouldBeCalledOnce();
-        $cache
-            ->getItem('3')
-            ->shouldBeCalledOnce();
-
-        $cache
-            ->getItem('0')
-            ->willReturn($cacheItemFound0);
-
-        $cache
-            ->getItem('1')
-            ->willReturn($cacheItemNotFound1);
-
-        $cache
-            ->getItem('2')
-            ->willReturn($cacheItemNotFound2);
-
-        $cache
-            ->getItem('3')
-            ->willReturn($cacheItemNotFound3);
-
-        $cacheItemFound0
-            ->isHit()
-            ->willReturn(true);
-
-        $cacheItemNotFound1
-            ->isHit()
-            ->willReturn(false);
-
-        $cacheItemNotFound2
-            ->isHit()
-            ->willReturn(false);
-
-        $cacheItemNotFound3
-            ->isHit()
-            ->willReturn(false);
-
-        $cacheItemNotFound1
-            ->set([1, 'b'])
-            ->shouldBeCalledOnce();
-
-        $cacheItemNotFound2
-            ->set([2, 'c'])
-            ->shouldBeCalledOnce();
-
-        $cache
-            ->save($cacheItemNotFound1)
-            ->shouldBeCalledOnce();
-
-        $cacheItemFound0
-            ->get()
-            ->willReturn([0, 'a']);
-
-        $cache
-            ->save($cacheItemNotFound1)
-            ->shouldBeCalled();
+        $this::fromResource($fhandle)
+            ->window(2)
+            ->shouldIterateAs([
+                [],
+            ]);
 
-        $cacheItemNotFound1
-            ->get()
-            ->willReturn([1, 'b']);
+        $fhandle = fopen(__DIR__ . '/../../fixtures/sample.txt', 'rb');
 
-        $cache
-            ->save($cacheItemNotFound2)
-            ->shouldBeCalled();
+        $this::fromResource($fhandle)
+            ->cache()
+            ->window(2)
+            ->shouldIterateAs([
+                [0 => 'a', 1 => 'b'],
+                [1 => 'b', 2 => 'c'],
+                [2 => 'c'],
+            ]);
 
-        $cacheItemNotFound2
-            ->get()
-            ->willReturn([2, 'c']);
+        $fhandle = fopen(__DIR__ . '/../../fixtures/sample.txt', 'rb');
 
         $this::fromResource($fhandle)
-            ->cache($cache)
+            ->cache()
             ->shouldIterateAs(['a', 'b', 'c']);
 
         $fhandle = fopen(__DIR__ . '/../../fixtures/sample.txt', 'rb');

src/Iterator/CacheIterator.php

@@ -0,0 +1,93 @@
+<?php
+
+declare(strict_types=1);
+
+namespace loophp\collection\Iterator;
+
+use Iterator;
+use Psr\Cache\CacheItemInterface;
+use Psr\Cache\CacheItemPoolInterface;
+
+/**
+ * @psalm-template TKey
+ * @psalm-template TKey of array-key
+ * @psalm-template T
+ *
+ * @implements \Iterator<TKey, T>
+ */
+final class CacheIterator implements Iterator
+{
+    /**
+     * @var CacheItemPoolInterface
+     */
+    private $cache;
+
+    /**
+     * @var Iterator
+     * @psalm-var Iterator<TKey, T>
+     */
+    private $inner;
+
+    /**
+     * @var int
+     */
+    private $key;
+
+    /**
+     * @psalm-param \Iterator<TKey, T> $iterator
+     */
+    public function __construct(Iterator $iterator, CacheItemPoolInterface $cache)
+    {
+        $this->inner = $iterator;
+        $this->cache = $cache;
+        $this->key = 0;
+    }
+
+    /**
+     * @psalm-return T
+     */
+    public function current()
+    {
+        return $this->getItemOrSave((string) $this->key)->get()[1];
+    }
+
+    /**
+     * @psalm-return TKey
+     */
+    public function key()
+    {
+        return $this->getItemOrSave((string) $this->key)->get()[0];
+    }
+
+    public function next(): void
+    {
+        ++$this->key;
+        $this->inner->next();
+    }
+
+    public function rewind(): void
+    {
+        $this->key = 0;
+    }
+
+    public function valid(): bool
+    {
+        return $this->cache->hasItem((string) $this->key) || $this->inner->valid();
+    }
+
+    private function getItemOrSave(string $key): CacheItemInterface
+    {
+        $item = $this->cache->getItem($key);
+
+        if (false === $item->isHit()) {
+            $item->set([
+                $this->inner->key(),
+                $this->inner->current(),
+            ]);
+
+            $this->cache->save($item);
+        }
+
+        return $item;
+    }
+}

src/Iterator/ClosureIterator.php

@@ -26,7 +26,7 @@ final class ClosureIterator extends ProxyIterator implements Iterator, OuterIter
 
     /**
      * @var callable
-     * @psalm-var callable(T...):(Generator<TKey, T>)
+     * @psalm-var callable(mixed...):(Generator<TKey, T>)
      */
     private $callable;
 
@@ -39,7 +39,7 @@ final class ClosureIterator extends ProxyIterator implements Iterator, OuterIter
     /**
      * @param mixed ...$arguments
      * @psalm-param T ...$arguments
-     * @psalm-param callable(T...):(Generator<TKey,T>) $callable
+     * @psalm-param callable(mixed...):(Generator<TKey,T>) $callable
      */
     public function __construct(callable $callable, ...$arguments)
     {

src/Operation/Cache.php

@@ -8,6 +8,7 @@
 use Generator;
 use Iterator;
 use loophp\collection\Contract\Operation;
+use loophp\collection\Iterator\CacheIterator;
 use Psr\Cache\CacheItemPoolInterface;
 use Symfony\Component\Cache\Adapter\ArrayAdapter;
 
@@ -25,49 +26,14 @@ public function __construct(?CacheItemPoolInterface $cache = null)
 
     public function __invoke(): Closure
     {
-        $iteratorIndex = 0;
-
         return
             /**
              * @psalm-param \Iterator<TKey, T> $iterator
              *
              * @psalm-return \Generator<TKey, T>
              */
-            static function (Iterator $iterator, CacheItemPoolInterface $cache) use (&$iteratorIndex): Generator {
-                for ($index = 0; true; ++$index) {
-                    $item = $cache->getItem((string) $index);
-
-                    if ($item->isHit()) {
-                        /** @psalm-var array{TKey, T} $value */
-                        $value = $item->get();
-
-                        yield $value[0] => $value[1];
-
-                        continue;
-                    }
-
-                    if ($iteratorIndex < $index) {
-                        $iterator->next();
-
-                        ++$iteratorIndex;
-                    }
-
-                    if (!$iterator->valid()) {
-                        break;
-                    }
-
-                    $item->set([
-                        $iterator->key(),
-                        $iterator->current(),
-                    ]);
-
-                    $cache->save($item);
-
-                    /** @psalm-var array{TKey, T} $value */
-                    $value = $item->get();
-
-                    yield $value[0] => $value[1];
-                }
+            static function (Iterator $iterator, CacheItemPoolInterface $cache): Generator {
+                return yield from new CacheIterator($iterator, $cache);
             };
     }
 }